Checking The Heater; Checking The Timer - Hisense RD-31WC4S series Service Manual

If there show 000 or no response then it is broken.

Checking the Heater

If defrost system failure，check the heater and the temperature fuse as well as wires.
Measuring temperature fuse and heater resistance about 361Ω then it is OK.( Blue and Yellow)

Checking the timer

Timer is an importance control component for air defrost refrigerator's defrost system. The common
problems as following: bad cooling, evaporator don't defrost or defrost incomplete. It's working
principle as following picture。